Associated luminescence centres and traps in the thermoluminescence of CaF2:Dy (TLD-200)

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Abstract
The thermoluminescence glow curve of CaF2:Dy TLD-200 extends from room temperature up to about 450 degrees C. Dy3+ is the main emitting centre for all the glow peaks. However, in addition to Dy3+ emission, the glow peaks above 325 degrees C show four extrabands in the region 250-600 nm. Three of these are attributed to Tb3+ and the fourth is possibly associated with the host lattice. The observations lead to the conclusion that all of the luminescent centres are not distributed randomly with respect to the traps. Some of these exist in the form of aggregates of traps and luminescent centres. The thermoluminescence resulting from the localized recombination within the aggregate centres leads to distinct spectral changes from one glow peak to another.